JP2010081603A - Method and node for implementing virtual network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable backward compatibility for cases where a mobile node has no virtual network capability. <P>SOLUTION: A network node for implementing a virtual network is configured to provide a plurality of m service providers to which another node may connect, the service providers having correspondingly different service provider identifiers. The network node includes a module for applying a plurality of k hash functions to each of the service provider identifiers, such that each of the hash functions, each time being applied to a certain service provider identifier, points to one bit to be set in a sequence of b bits. The sequence of the b bits thereby forms a compressed indication of the service provider identifiers. The network node further includes a module for repeatedly transmitting a beacon comprising the compressed indication of the service provider identifiers to advertise the service providers provided by the network node. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and a node for realizing a virtual network.

When network virtualization is performed, the current networking paradigm is shared between a network provider (NP) and a service provider (SP). Here, a network provider provides an infrastructure and supports one or several service providers on the infrastructure. This paradigm sharing extends from core network routers to leaf routers or access points (APs). The latter typically advertises service providers with periodic beacons, and the mobile node scans the beacons before associating with the desired AP. In current virtual LANs (VLANs), a first solution is that the AP simply sends one beacon or SSID for every (virtual) service provider. Alternatively, as a second solution, the AP has a notified primary SSID and a secondary SSID, and the mobile node transmits a probe request to the secondary SSID. Both of these solutions have the following disadvantages:
-Sending one beacon or SSID to each service provider (SP) supported by the network provider (NP), especially when the network provider (NP) supports multiple service providers (SP) waste. These SPs can be announced dozens of times per second over weeks, months, or years without being used by any mobile node.
Solutions that beacon the primary SSID and provide the secondary SSID “on demand” will cause their probe requests to compete with normal data traffic. By actively requesting a secondary SSID and competing with the data traffic, significant delays will occur before establishing a new association. This is disadvantageous when roaming.

  At present, the most relevant and widely known method for virtual networks is the Cisco VLAN solution. In this solution, the primary SSID is broadcast by the AP. As soon as the mobile station overhears the primary SSID, it sends a probe request asking if the AP supports a “secondary SSID”, ie a virtual network.

  This solution has been successful in supporting multiple virtual or secondary SSIDs with a single primary SSID while maintaining backward compatibility. However, nodes need to compete to access the channel and send their probe requests, which delays the node from associating to the network.

In order to solve the above problems, the present invention provides a network node for realizing a virtual network. The network node provides a plurality of m service providers to which another node may connect, where m is a natural number greater than zero, and the plurality of service providers are different from each other. Has a service provider identifier,
A module for applying a plurality of k hash functions to each of the plurality of m service provider identifiers, wherein k is a natural number greater than zero, and the plurality of k hash functions Each hash function of each indicates one bit in a b-bit sequence each time it is applied to each service provider identifier, and the indicated bit is set by the module, whereby the b-bit sequence A module adapted to form a compressed indication of the service provider identifier of the service provider provided by the network node; and
A module for repeatedly transmitting a beacon including the compressed indicator of the service provider identifier of the service provider to announce a service provider provided by the network node.

  The compressed indication of the service provider identifier saves bandwidth and is backward compatible.

  According to the present invention, the network node generates a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm, and transmits the checksum to the beacon transmitted by the network node. A module for including a checksum is further provided.

  This allows the mobile node to check whether the CSSIDs actually indicate multiple service providers.

  According to the invention, the network node has a service with a mobile node based on the compressed indicator of the service provider identifier as if the compressed indicator is an indicator of a single service provider. When a connection to a provider is to be made, a module is further provided to forward to the mobile node a service provider indication that can be used in the network node by unicast.

  This ensures backward compatibility when the mobile node does not support the virtual network.

In order to solve the above-described problems, the present invention also provides a node that can be connected to a network node that realizes a virtual network. Here, in the virtual network, the network node provides a plurality of m service providers to which the node may connect, where m is a natural number greater than zero, Each service provider has a different service provider identifier.
The node is
A module for overhearing a beacon transmitted by the network node to announce the plurality of m service providers;
A module for applying a plurality of k hash functions to a service provider identifier that the node wishes to connect to, wherein k is a natural number greater than zero, and each of the k hash functions When the hash function is applied to the service provider identifier that the node wishes to connect to, the hash function indicates one bit to be set in the b-bit sequence, and the bit group set by applying the hash function and the Comparing a corresponding bit group in a sequence of b bits included in a beacon received from a network node, wherein the b bit in the beacon is a compressed indication of the service provider identifier provided by the network node And the corresponding bit group is set by the module. When it is detected that there is provided a a module in which the service provider to which the node corresponding to the service provider identifier to which you want to connect conclude that being provided by the network node,
The module for applying the hash function repeats the application of the k hash functions and the comparison of the bit group for each service provider identifier corresponding to the service provider that the node wants to connect to. ,
The node further comprises a module for attempting to establish a connection with one of the service providers concluded to be provided by the network node.

  As a result, a mobile node that uses the compressed index of the service provider identifier can be realized.

According to the present invention, the node is a module for identifying a b-bit part that is a compressed indicator of service provider identifiers of several service providers provided by the network node in a beacon received from the network node. Is further provided.
The identifying module further generates a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm, and the generated checksum is included in a beacon transmitted by the network node. And, if the two chuck sums match, is configured to conclude that the compressed indicator of the service provider identifier is actually an indicator of multiple service providers. .

  Based on the compressed indicator of the service provider identifier, the node tried to connect to a service provider with the node as if the compressed indicator was a single service provider indicator, A module for receiving in unicast from the network node an indication of the service provider available at the network node if it fails to connect because it actually indicates multiple service providers; ing.

In order to solve the above problems, the present invention also provides a method for realizing a virtual network. Here, a network node in the virtual network provides a plurality of m service providers to which another node may connect, m is a natural number greater than zero, and the plurality of service providers are , Each having a different service provider identifier.
The method is
Applying a plurality of k hash functions to each of the plurality of service provider identifiers, wherein k is a natural number greater than zero, and each hash function of the plurality of k hash functions is represented by each service provider Each time it is applied to an identifier, it points to one bit to be set in the b-bit sequence, so that the b-bit sequence represents a compressed indicator of the service provider identifier of the service provider provided by the network node. Steps to be formed, and
Repeatedly transmitting a beacon including the compressed indication of the service provider identifier of the network provider to announce a service provider provided by the network node.

  The method further includes generating a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm and including the checksum in a beacon transmitted by the network node.

  The method is based on a compressed indicator of the service provider identifier, when a mobile node is trying to connect to a service provider as if the compressed indicator is a single service provider indicator The method further includes the step of unicasting to the mobile node an indication of a service provider available at the network node.

In order to solve the above problems, the present invention also provides a method for connecting a node to a network node that realizes a virtual network. Here, in the virtual network, the network node provides a plurality of m service providers to which the node may connect, m is a natural number greater than zero, and the plurality of service providers are , Each having a different service provider identifier.
The method is
The node overhears a beacon transmitted by the network node to announce the plurality of m service providers;
Applying a plurality of k hash functions to a service provider identifier of a service provider that the node wishes to connect to, where k is a natural number greater than zero, and the k hash functions Each hash function points to a bit to be set in a b-bit sequence when applied to the service provider identifier of the service provider that the node wishes to connect to, and is set by applying the hash function And a corresponding bit group in a sequence of b bits included in a beacon received from the network node, the b bit in the beacon being a service provider service provided by the network node Form a compressed indicator of the provider identifier , If the node detects that the corresponding bit group is set, the service provider wants the node is connected to conclude that being provided by the network node, the steps,
Repeating the application of the k hash functions and the comparison of bit groups for each service provider identifier corresponding to the service provider that the node wishes to connect;
Attempting to establish a connection with one of the service providers concluded to be provided by the network node.

The method is
Identifying a b-bit portion that is a compressed indicator of a service provider identifier of a service provider provided by the network node in a beacon received from the network node;
Generating a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm;
Comparing the generated checksum to a corresponding checksum in a beacon transmitted by the network node;
If the two chuck sums match, the method further comprises the step of concluding that the compressed indicator of the service provider identifier is actually an indicator of a plurality of service providers.

  The method attempted to connect to a service provider with the node based on the compressed indicator of the service provider identifier as if the compressed indicator was a single service provider indicator, The mobile node receives a unicast from the network node of service provider indications available at the network node if the connection fails because it actually indicates multiple service providers; In addition.

  In order to solve the above problems, the present invention also provides a computer program having computer program code that enables the method of any of the above aspects to be executed when executed on a computer.

It is the schematic which shows the notification of the service provider by a prior art. FIG. 6 is a schematic diagram illustrating further possible service provider announcements according to the prior art. It is the schematic which shows operation | movement of the node by one Embodiment of this invention.

First, some terms used in the following description are defined.
AP (Access Point): Access point NP (Network Provider): Network provider SP (Service provider): Service provider SSID (Service Set IDentifier): Service set identifier VLAN (Virtual LAN): Virtual LAN

  According to one embodiment, the proposed new solution consists of aggregating several SP SSIDs (or service provider identifiers) supported by a given NP into a Bloom Filter. The Bloom filter can be thought of as a “compressed list” that the AP periodically announces, and the mobile node checks whether their SSID is included in the compressed list.

  To that end, the mobile node applies the Bloom filter to the service provider identifier of the service provider that it wishes to connect to. This results in a bit pattern that the mobile node checks to see if the same bits are set in it by comparing it to the received Bloom filter output received by the mobile node from the access point. it can. Here, if the same bit group is set, this means that the service provider identifier is included in the compression list generated by the Bloom filter.

  Such an approach has several advantages, including:

  Since there is no need to advertise one SSID for each service provider, this solution can be used for beaconing in virtual networks, especially when the number of SPs is large and a specific SP needs to be advertised but rarely used. Make (beaconing) highly efficient.

  In addition, the solution is based on passive scanning of the announced SSID list (bloom filter), so there is no need to request a secondary SSID and no need to compete to access the channel. The time required for the association is short, which is very advantageous when roaming.

  Furthermore, the solution is backward compatible in the sense that existing mobile nodes can still function without requiring an update. However, in order to implement the proposed approach, the AP and virtual network capable nodes need to be updated.

  Finally, this approach requires only software changes to existing systems (no hardware changes are required).

  Hereinafter, embodiments of the present invention will be described in more detail. In this context, embodiments are described for an IEEE 802.11 network without compromising generality and to make the description more specific. However, the general concept can be applied to any radio access technology.

  To help a mobile node or phone find an AP with which it can associate, the AP periodically sends a network ID (SSID) in a form that is contained within a beacon that is regularly sent every 100 ms. To announce. In the upper part of FIG. 1, regular transmissions of beacons such as T = 0, T = 1, T = 2 are shown. In the middle part of FIG. 1, the format of the beacon is shown. This format has a format that starts with a MAC header and then continues with the frame body of the beacon. The lower part of FIG. 1 shows the detailed contents of the frame body of the beacon. The fourth item of the frame body of the beacon is the SSID that announces the NP ID in the embodiment of the present invention.

  By overhearing those beacons, the mobile node can find new networks, estimate the link quality for each network, and whether it can establish an association to the new network or AP Can be determined.

Most APs currently deployed are operated by separate network providers without support for virtualization. However, this approach has been shown to be costly and not optimal for the following reasons in a scenario where multiple operators coexist.
-When radio resources are used together, there is a problem because the number of non-interfering channels may be reduced.
Introducing multiple APs in a given area (eg airport) can be burdensome and undesirable.
・ Each operator generally has a low utilization rate, which increases the cost of introducing wireless channels and infrastructure.

  The current trend is to have multiple network service providers (SPs) that actually provide services to customers supported by a network provider (NP) that actually owns the network infrastructure. This separation concept extends from the core of the network to the end router or AP. This concept is widely understood by network operators and service providers who can create more benefits of infrastructure while more efficiently using bandwidth (wireless or wired). This concept is called “virtual network” and is the basic element of next generation network.

  Just like the network that is now widespread, the network provider's AP needs to periodically announce the network identifier using its beacon. These beacons contain the SSID (service set identifier) of the supported SP, and the mobile node can overhear such beacons and perform an association to the desired AP.

  If an AP wants to announce multiple service providers (not just the network provider NP), several solutions to this problem could be envisaged.

  A very intuitive solution for maintaining backward compatibility of network nodes and mobile nodes may be to keep one SSID per beacon. For a given SSID per SP, the beacon interval can be maintained as in a non-virtual network. Therefore, when the number of SPs becomes n, the beacon density increases just n times, and as a result, the bandwidth available for actual data traffic decreases significantly.

  Another option would be to keep sending beacons at the same rate as in non-virtual networks. In this case, a given SSID of the SP is broadcast every n beacon periods. If a network provider supports multiple service providers, it may take a long time for a particular SSID to be broadcast again. This results in a long delay before the mobile node finds the desired network that it wants to establish an association with. The network situation will get worse when roaming.

  FIG. 2 schematically shows two possible solutions. The upper part of FIG. 2 shows three possible ways of setting the beacon timing. At times T = 0, T = 1, T = 2 and T = 3, a beacon of a particular SP SSID is shown. Here, the SSID beacon of a particular SP is shown as an empty box on the horizontal arrow in the portion surrounded by the upper square in FIG. Immediately below that empty box is shown a first method that incorporates two additional SSIDs, one shown as a vertical box and the other as a horizontal box. Yes. The added first box is transmitted at timing T = 1, and the added second box is transmitted at timing T = 2. This means that if there are n different SSIDs, the repeat interval of a specific beacon swells n times, resulting in a delay time, which is disadvantageous in the case of roaming, for example.

  In FIG. 2, another approach is shown further below what has just been described. In this approach, a second beacon (vertical line box) is transmitted immediately after T = 0, followed by a third type of beacon (horizontal line box). This means that all three types of beacons are transmitted after T = 0 and before T = 1, resulting in an increase in temporal beacon density.

  In both situations described above, SSIDs will continue to be broadcast every 10 or 100 ms even when some of them are rarely used, which is clearly inefficient. In this exemplary situation, a network provider in country X may support provider Y's service. Even if the customer of provider Y rarely visits country X, the network provider AP in country X needs to announce Y's SSID every 10 or 100 ms.

  To overcome this inefficiency problem, the solution implemented in the Cisco virtual LAN utilizes a primary SSID and a secondary SSID. The primary SSID is an SSID announced by the AP and is overheard by the mobile node. The mobile node then sends a probe request that queries the AP for a specific (secondary or virtual) SSID. This approach solves the inefficiency problem, but has the problem that the probe request must be competing with all other traffic, including data traffic, before being sent on the channel. If a mobile node is a member of m virtual networks, it must actively probe for each SSID of m SSIDs until it finds the desired SP.

  FIG. 2 shows a further approach of adding two SSIDs at the fourth item of the beacon frame body. For example, it can be considered to include a plurality of SSIDs in this place. However, such an approach may break backward compatibility.

  A solution according to an embodiment of the invention is to replace the SSID in the broadcast beacon with a Bloom filter that includes all SSIDs of supported service providers (SPs). The Bloom filter is a set of b bits (b bit group) and can be thought of as a compressed list for the mobile node to search for a desired SSID. Before going into the detailed description of the embodiment, the Bloom filter will be described.

  A Bloom filter is a set of b bits that can check whether a given entry is found. It should be noted that a complete list of entries cannot be retrieved, but a Boolean check can be performed to see if an entry exists.

  To include an entry in the Bloom filter (in our case, the AP wants to include a given SSID), a set of k hash functions is applied to that entry. The result of every hash function is a bit position in the b-bit filter, where the bit will be set to 1 (all bits are initially set to 0) ing). Every entry is input to a (k) hash function, and every hash function points to a bit position in the (b-bit) Bloom filter, which is set to 1.

  To check if an entry exists in the Bloom filter (in our case, the mobile node checks if a particular SSID is present in the Bloom filter announced by the AP) The reverse operation is performed. First, an entry is input to the same (k) hash functions. Next, the bit positions pointed to by these hash functions are checked. At this time, if they are all 1, it can be concluded that the entry exists in the Bloom filter (this means that the SSID has been announced by the AP).

If a Bloom filter is used, false detection may occur. For example, it is checked that the bit group of entry_3 is all 1, and as a result, it may be determined that entry_3 does not actually exist but exists in the Bloom filter. This occurs when the bit position of entry_3 is a combination of bit positions of different entries (eg, entry_1 and entry_2). False detection using the Bloom filter
(1-e- ^km / ^b ) ^k
It happens with the probability of In the above equation, k is the number of hash functions, and b is the filter size (number of bits). M is the number of entries included in the Bloom filter.

  Conversely, a missed detection (when an entry is reported as not included but actually included in the Bloom filter) never occurs.

  After this description of the Bloom filter, their application examples in one embodiment of the present invention will now be described in detail.

  According to one embodiment, the Bloom filter is used as a compressed list of one or several SSIDs that the AP wishes to broadcast. Each service provider i supported by the network provider has a SSID_i. The network provider inputs all SSIDs into k hash functions (see FIG. 3). At this time, each hash function indicates a specific position in the b-bit Bloom filter, and the bit at that position is set to 1. As a result, the Bloom filter is a “compressed list” of SSIDs, and the mobile node uses this list to perform a bit check on the position corresponding to the hash value of SSID_i, and SSID_i is in the compressed list. It can be checked whether or not it exists.

  FIG. 3 schematically shows this procedure. There are m different SSIDs (SSID1 to SSIDm) of m (or n) different service providers. All of these service providers use the infrastructure of the network provider NP. These service identifiers SSID need to be notified by beacons by the NP, and for that purpose, a b-bit Bloom filter is generated as follows. First, k hash functions h_1 () to h_k () are applied to each SSID. Each result of applying these hash functions sequentially points to one of the bits of the b-bit Bloom filter. The bit thus pointed is set (to 1), and k bits are set (to 1) as a result of applying k hash functions to SSID1. The same procedure is executed from the second SSID (SSID2) to the mth SSID (SSIDm). Eventually, p ≦ m × k bits of the b-bit Bloom filter are set (to 1), and the result can be regarded as a combined list of SSIDs.

  The resulting combined list of SSIDs (hereinafter abbreviated as CSSIDs) is then linked to a checksum as shown in FIG. This checksum indicates whether the overheard mobile station is a combination of some other SSID (in other words, a combined SSID indicating a virtual network or just a “normal” SSID). It can be regarded as an indication that can be checked on the basis of.

  The simplest method for indicating whether the SSID is a “normal SSID” or a virtual network (“combined SSID”) is set for a virtual network but for a non-virtual network One bit that is not set is reserved. However, it may happen that such a bit happens to be set by a very normal SSID in a “classic” legacy network. This approach is therefore less preferred. A more preferred solution is to utilize a “real” checksum that is calculated based on the bit sequence of the combined SSID using some checksum generation algorithm. One possibility is to use a hash function. However, any other algorithm (eg, CRC-8, CRC-32, etc.) that produces predictable and reproducible results based on the CSSID and can be used as a checksum can also be used. If such a “real” checksum generation algorithm is used, the probability that a “normal” SSID will be mistaken for a virtual network index (or CSSID) is very low. According to an embodiment, there is a predetermined length b bits of the Bloom filter (CSSID) and a specified length p bits of the checksum. As a result, the mobile node that receives the notification determines the SSID in the received beacon. Know where to look for (b bit part) and where to checksum (p bit part).

  As shown at the bottom of FIG. 3, the combination of the combined SSID (combined SSID) and the checksum (CSSIDs || checksum) is placed in the SSID field of the beacon that is periodically broadcast by the AP.

  The mobile node corresponding to the virtual network can (passively) obtain (CSSIDs || checksum). According to one embodiment, the mobile nodes first checksum generation algorithms for what they consider a CSSID (in one embodiment, by definition, the mobile nodes know as virtual network-enabled nodes). To checksum = checksum (CSSIDs). As a result, if it matches the checksum of the received beacon, the mobile node will know (with a low error rate) that it is a combination of virtual SSID and not a non-virtual network SSID. Next, it is checked whether or not the own SSID (the SSID that the user is looking for) exists in the CSSID. For that purpose, it applies the hash function in the same way as already described, in other words as if it wants to generate a b-bit Bloom filter based on the SSID it is looking for. This sets k bits in the resulting b-bit Bloom filter (because the Bloom filter uses k hash functions). These k bits are then checked as to whether the corresponding bit in the b-bit Bloom filter received in the beacon is also set. If set, the mobile node that received the beacon can conclude that the service provider corresponding to the SSID that it was looking for was announced by the AP. Therefore, the SSID can be used for the mobile node to connect to the AP. This check is then repeated for all SSIDs to which the mobile node can belong or that the mobile node is looking for (eg, if the mobile node is registered with multiple service providers, the mobile node May look for multiple SSIDs).

  The check is done by passively overhearing (CSSIDs || checksum), so that the association of the entire mobile node is compared to the prior art based on sending probe requests for every SSID. You will understand that it is faster. Probe requests typically compete with other traffic, including data traffic. For this reason, the delay of association may increase, and the performance at the time of roaming may deteriorate significantly.

  For mobile nodes that do not support virtual networks, they consider the announced (CSSIDs || checksum) as a regular SSID that they can associate with.

  However, mobile nodes that do not support virtual networks cannot distinguish the “true” SSID from the CSSID, so one possibility is to alternately announce the CSSID and the “classic SSID” of the network provider. Conceivable. For example, for every one or two or n beacons containing a CSSID, the SP's SSID can be announced in a classic manner. By doing so, a normal mobile node can usually still find an SSID that is combined with other things and can connect to the AP using this SSID.

  This can be applied, for example, when the mobile node is looking for a specific SSID (such as SSID = DOCOMO). This mobile node does not support virtualization so that its specific SSID can be read from the combination SSID, for example because it has not yet been upgraded by the operator. In this case, one possible solution according to an embodiment is to alternate between regular SSID and combined SSID at very (or relatively) long time intervals. This is a kind of intermediate solution (compromise) between 100% regular (non-combined) SSID and 100% combined SSID.

  Another possibility is that a mobile node that mistakes the CSSID for a regular SSID attempts to connect to the service provider as if the CSSID is a regular SSID. Such a request can be processed by the AP, for example in a way that the AP sends a “true SSID” in unicast, or a network available to the mobile node so that the mobile node can initiate a connection. Can be processed by selecting.

  A mobile node that has overheard (CSSIDs || checksum) has not been able to see the ID of the network provider NP. The NP ID can be selectively requested by the mobile node by using an additional probe request, and the reply (response) includes the NP ID.

  Finally, it should be emphasized that the above embodiment requires only software changes, whether on the AP side or on the mobile node side. Generally speaking, after checking whether the checksum =? Checksum (CSSIDs) is correct or not, in the device driver, the check (SSID_of_mobile node =? SSID_broadcasted_by_AP) is replaced with a check (SSID_of_mobile node in? CSSIDs). The processing cost of the check (SSID_of_mobile node in? CSSIDs) is equal to the processing cost of the k hash functions, which can generally be ignored, and added even though the beacon announces two or more SPs There is no network load.

  In order to show an example of the gain and false detection of the proposed method, an example of an IEEE 802.11 standard network to which an aggregated beaconing method is applied is introduced.

  A beacon is typically 50 bytes long. When transmitted at 1 Mbps, it takes 0.4 milliseconds (ms). For example, if the NP supports 50 SPs, 50 SSIDs need to be announced. If announced separately (1 SSID or beacon for backward compatibility), it takes 20 milliseconds, which corresponds to 20% of the beacon period. According to the proposal, the aggregated SSID fits in the SSID field within a single beacon and thus takes 0.4 milliseconds, ie 0.4% of the beacon period.

As already mentioned, in this proposal, mobile nodes that do not support the virtual network can coexist with those that support the virtual network, and no changes are required to their software or hardware. Is backwards compatible in the sense that it can work. This is due to the following.
• This proposal does not require any changes to the standard beacon format.
There is no change in standard protocol behavior, ie beaconing, association request, association, data transmission, and disassociation.

  Implementation of the proposal can be performed by updating the software of the network provider's AP and the software of the service provider's node to support the proposed method with respect to, for example, a combination of SSIDs.

  The above description has been made in connection with the IEEE 802.11 standard network, the main idea is applicable to any other network, and the service provider identifier is the SSID in the sense of the IEEE 802.11 standard network. It will be understood that this need not be the case.

DA frame destination SA frame source BSSID Basic service set identifier FCS frame check sequence SSID Service provider identifier

Claims (13)

A network node for realizing a virtual network, which provides a plurality of m service providers to which another node may connect, where m is greater than zero A natural number, and each of the plurality of service providers has a different service provider identifier;
A module for applying a plurality of k hash functions to each of the m service provider identifiers, wherein k is a natural number greater than zero, and each hash function of the k hash functions Refers to one bit in the b-bit sequence as it is applied to each service provider identifier, and the indicated bit is set by the module so that the b-bit sequence is A module adapted to form a compressed indicator of a service provider identifier of a service provider provided by the node; and
A module for repeatedly transmitting a beacon including the compressed indicator of the service provider identifier of the service provider to announce a service provider provided by the network node.   A module for generating a checksum using a checksum generation algorithm based on a compressed indicator of the service provider identifier and further including the checksum in a beacon transmitted by the network node. Item 4. The network node according to Item 1.   Based on the compressed indication of the service provider identifier, if the mobile node is trying to connect to a service provider as if the compressed indication is that of a single service provider The network node according to claim 1 or 2, further comprising a module for unicasting an indicator of a service provider available in the network node to the node. A node that can be connected to a network node that realizes a virtual network, wherein the network node in the virtual network provides a plurality of m service providers to which the node may connect; Here, m is a natural number greater than zero, and the plurality of service providers have different service provider identifiers,
A module for overhearing a beacon transmitted by the network node to announce the plurality of m service providers;
A module for applying a plurality of k hash functions to a service provider identifier that the node wishes to connect to, wherein k is a natural number greater than zero, and each of the k hash functions When the hash function is applied to the service provider identifier that the node wishes to connect to, the hash function indicates one bit to be set in the b-bit sequence, the bit group set by applying the hash function, Comparing a corresponding bit group in a sequence of b bits included in a beacon received from a network node, wherein the b bit in the beacon is a compressed indication of the service provider identifier provided by the network node And the corresponding bit group is set by the module. When it is detected that there is provided a a module in which the service provider to which the node corresponding to the service provider identifier to which you want to connect conclude that being provided by the network node,
The module for applying the hash function repeats the application of the k hash functions and the comparison of the bit group for each service provider identifier corresponding to the service provider that the node wants to connect to. ,
The node further comprises a module for attempting to establish a connection with one of the service providers concluded to be provided by the network node. A module for identifying a b-bit portion that is a compressed indicator of a service provider identifier of a service provider provided by the network node in a beacon received from the network node;
The identifying module generates a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm, and the generated checksum is transmitted in the beacon transmitted by the network node. The identifying module compares the corresponding checksum, and if the two chuck sums match, the compressed indicator of the service provider identifier is actually a plurality of service provider indicators. The node of claim 4, wherein the node is configured to conclude.   Based on the compressed indicator of the service provider identifier, the node tried to connect to a service provider as if it were a single service provider indicator, but that actually A module for receiving, by unicast, an indication of a service provider that can be used in the network node in a case where a connection fails due to a plurality of service providers. The node according to 4 or 5. A method for realizing a virtual network, wherein a network node in the virtual network provides a plurality of m service providers to which another node may connect, where m is zero A larger natural number, the plurality of service providers each having a different service provider identifier;
Applying a plurality of k hash functions to each of the plurality of service provider identifiers, wherein k is a natural number greater than zero, and each hash function of the plurality of k hash functions is represented by each service provider Each time it is applied to an identifier, it points to one bit to be set in the b-bit sequence, so that the b-bit sequence represents a compressed indicator of the service provider identifier of the service provider provided by the network node. Steps to be formed, and
Repeatedly transmitting a beacon including the compressed indication of the service provider identifier of the network provider to announce a service provider provided by the network node.   8. The method of claim 7, further comprising: generating a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm and including the checksum in a beacon transmitted by the network node. the method of.   Based on the compressed indication of the service provider identifier, if the mobile node is trying to connect to a service provider as if the compressed indication is a single service provider indication, the mobility 9. A method according to claim 7 or 8, further comprising the step of unicasting to a node an indication of a service provider available at the network node. A method for connecting a node to a network node that implements a virtual network, wherein the network node in the virtual network provides a plurality of m service providers to which the node may connect. , Where m is a natural number greater than zero, and the plurality of service providers each have a different service provider identifier;
The node overhears a beacon transmitted by the network node to announce the plurality of m service providers;
Applying a plurality of k hash functions to a service provider identifier of a service provider that the node wishes to connect to, where k is a natural number greater than zero, and the k hash functions Each hash function points to a bit to be set in a b-bit sequence when applied to the service provider identifier of the service provider that the node wishes to connect to, and is set by applying the hash function And a corresponding bit group in a sequence of b bits included in a beacon received from the network node, the b bit in the beacon being a service provider service provided by the network node Form a compressed indicator of the provider identifier , If the node detects that the corresponding bit group is set, the service provider wants the node is connected to conclude that being provided by the network node, the steps,
Repeating the application of the k hash functions and the comparison of bit groups for each service provider identifier corresponding to the service provider that the node wishes to connect;
Attempting to establish a connection with one of the service providers concluded to be provided by the network node. Identifying a b-bit portion that is a compressed indicator of a service provider identifier of a service provider provided by the network node in a beacon received from the network node;
Generating a checksum based on a compressed indicator of the service provider identifier using a checksum generation algorithm;
Comparing the generated checksum to a corresponding checksum in a beacon transmitted by the network node;
The method of claim 10, further comprising: if the two chuck sums match, concluding that the compressed indicator of the service provider identifier is actually a plurality of service provider indicators.   Based on the compressed indicator of the service provider identifier, the node tried to connect to a service provider as if it were a single service provider indicator, but that actually The mobile node further receives a unicast indication from the network node of an indication of a service provider available at the network node if the connection fails due to indicating a plurality of service providers. The method according to 10 or 11.   A computer program having computer program code which, when executed on a computer, makes it possible to carry out the method according to any one of claims 7 to 12.